---
title: "-=(_:_:)"
framework: swift
role: symbol
role_heading: Operator
path: "swift/duration/-=(_:_:)"
---

# -=(_:_:)

Subtracts the second value from the first and stores the difference in the left-hand-side variable.

## Declaration

```swift
static func -= (lhs: inout Duration, rhs: Duration)
```

## Parameters

- `lhs`: A numeric value.
- `rhs`: The value to subtract from lhs.